A reference voltage generation circuit is in wide use as a power source for driving a semiconductor device stably. The reference voltage generation circuit is a constant voltage source for generating a reference voltage Vref within the semiconductor device which does not depend on a power supply voltage VDD outside the semiconductor device. This type of reference voltage generation circuit may undergo a startup failure of the circuit, that is, may have zero output voltage at startup of the circuit, because depending on the circuit configuration, the output of a reference voltage generation unit which directly generates the reference voltage Vref has two values as solutions, i.e., 0V (with respect to GND) and the reference voltage Vref being a specified voltage. Such a startup failure could occur in a circuit of a mode in which the reference voltage Vref serving as the output voltage is provided as feedback to the reference voltage generation unit. With such a type of reference voltage generation circuit, therefore, a startup circuit unit is integrally connected to the reference voltage generation unit generating the reference voltage Vref and, at the startup of the circuit, a predetermined current is flowed into the reference voltage generation unit by the startup circuit unit to start the circuit.
As publicly known documents which disclose a reference voltage generation circuit formed by integration of a reference voltage generation unit and a startup circuit unit, Patent Documents 1 and 2, for example, are present.